1. Field of the Invention
The invention relates to a capacitive switch of a kind used in a large number of applications. A capacitive field generated by a copper layer radiates in the direction of a user interface. As soon as the capacitive field is disrupted, for example, by being penetrated by a human finger, the field value changes. An integrated circuit arranged adjacent and close to the copper layer permanently measures these changes in the capacitive field, with the effect that an electrical switching signal can be generated by means of a microcontroller that is electrically connected to the integrated circuit when the capacitive field of the copper layer rises above or drops below a preset limit value.
2. Description of the Prior Art
It has proved to be disadvantageous in a capacitive switch of this kind that it cannot be used in electrical devices which have to fulfill a certain safety requirement. For example, false switchings can arise because the integrated circuit no longer functions correctly after a certain service life, or because the synchronisation of interrogating the capacitive field from the copper layer is disrupted because of the integrated circuit of the microcontroller that controls the integrated circuit and picks up its signals. Other incorrect switchings arise if the capacitive field is inadvertently disrupted, for example, in the boundary area, when there was no intention for the capacitive field to be influenced.
If an incorrect switching of the capacitive switch occurs and the switch is used as a movement initiator for a machine tool, then the control unit of the machine tool will not function or it will be controlled in a fully inadvertent manner. Consequently, this can lead to possibly serious accidents or other malfunctions in operation; possibly, the function of the machine tool will be significantly impaired as a result.
Therefore, for many years now, there has been a significant need for the capacitive switches of the prior art to be made capable of being used in other electrical devices as well, the switching and control functions of which should take place reliably and on a continuous basis, because these capacitive switches have to demonstrate a certain level of switching security.